1. Field of the Invention
The present invention relates to a radiation imaging apparatus in which at least an imaging plate, an image data memory, and a power supply unit are accommodated in a closed housing, and a cradle in which the radiation imaging apparatus is accommodated. The imaging plate, in which pixels in which charges are accumulated by receiving a radiation are two-dimensionally arrayed, takes an image based on the radiation. The image data memory stores data of the image taken by the imaging plate. The power supply unit supplies an electric power to the imaging plate and the image data memory.
2. Related Art
For example, Japanese Patent No. 3494683 discloses a radiation imaging apparatus (also referred to as a cassette for radiation detector or electronic cassette) in which a radiation detector and an image memory are incorporated. In the electronic cassette, a radiation image detected by the radiation detector is stored as image data in the image memory, the image data read from the image memory is converted into a wireless signal, and the wireless signal is output to an external signal processing circuit.
Because the electronic cassette is used in medical field, the housing has an closed structure from the standpoints of good hygiene and radiation handling. For example, Japanese Patent Application Laid-Open (JP-A) No. 2001-224579 discloses the closed structure.
On the other hand, the electronic cassette requires a measurable amount of electric power, it is necessary to reduce the power consumption. For example, JP-A No. 2005-7086 proposes a technique for the purpose of the reduction of the power consumption. In the technique, a capacitance amount of a battery provided in the closed structure is monitored, and the electronic cassette switches to a power saving mode to avoid the unnecessary power consumption when the capacitance amount becomes a predetermined value or less.
However, sometimes the electronic cassette is suddenly used in an emergency in the field of emergency medical care. In such emergency situation, unfortunately a response to the emergency situation cannot be given unless the battery of the electronic cassette is sufficiently charged. One of the reasons why the response to the emergency situation cannot be given is that quick charge cannot be performed, because, if the housing of the electronic cassette has the closed structure, the battery is inevitably charged by non-contact charge.
Even if the electronic cassette switches to the power saving mode due to the decreased capacitance amount of the battery, a battery lifetime is merely lengthened in the state of the decreased capacitance amount of the battery, and the response to the emergency situation is insufficiently given.